Studies on protein structure and function, on the nature of blood and tissue antigens, and on the mechanism of enzyme action or blood coagulation frequently require large amounts of highly purified proteins. However, even when satisfactory isolation methods are available, the average laboratory is equipped to prepare only small quantities of material. The National Fractionation Center, established in 1970 within the Blood Research Laboratory of the American Red Cross, has access to blood, plasma and Cohn fractions produced by the Blood Program as source material as well as pilot-plant facilities and the staff necessary for moderately large scale (40 liters) fractionation. The Center prepares plasma proteins and other blood components on request for distribution to qualified investigators and also distributes a large number of various plasma fractions generated either through commercial fractionation of the Red Cross plasma or through its own research activities. In order to meet the increasing demand for purified proteins, continued support for the Center is requested. In addition, the Center will continue its effort to develop a completely new system for large scale plasma fractionation using non-denaturing reagents and techniques to allow recovery and utilization of many labile proteins which are destroyed by conventional fractionation techniques.